Regardless of what some people say, FFOF is a pretty good soil. You can run a complete cycle without adding ANY nutrients. Maybe not in 3 gal, but I've done it with success in 7 gal.Fox Farm ocean forest..3 gal...GH Flora Micro,bloom and kool bloom.
But when you run a lengthy vedge, with heavy feeders, small containers, nutrients will be depleted towards the end.
Since you have been feeding them along the way, how much of the organic nutrients remain in the soil now? IDK.
If it was me, I'd want at least the last 1-2 weeks before chop with no fertilizer added.
What's left in your soil (organic and synthetic) will easily carry them that far.
I think it will end up being closer to 70 day vs. 50-60.
Good luck and I'm sure you'll do well.